1. Field of the Invention
This invention relates to a spark ignition internal combustion engine having a sub-combustion chamber into which a gas mixture is supplied. The gas mixture has an air-fuel ratio adapted for an engine operating state over a wide operating range of the engine. In the present invention, the engine has a high operating efficiency, and an amount of hydrogen carbide discharged is lowered.
2. Description of the Background Art
A spark ignition internal combustion engine is known in which supplied gas is formed in a layer within a combustion chamber from a rich gas mixture to a lean gas mixture under a low load operation state of the engine. The rich gas mixture is ignited by a spark plug, and the gas mixture with an average lean air-fuel ratio is completely ignited in such a way that no unignited gas is produced (refer to a gazette of Japanese Patent Publication No. Sho 47-43368).
In the internal combustion engine described in the above gazette, a pressure accumulating chamber filled with pressurized air, a sub-combustion chamber, a main combustion chamber, a communicating opening to cause both sub-combustion chamber and main combustion chamber to be communicated to each other, and a poppet valve communicating the pressure accumulating chamber and the sub-combustion chamber in such a way that they may be opened or closed are arranged in a straight line. In this way, gas mixture in the pressure accumulating chamber is injected into the sub-combustion chamber through the poppet valve released near a top dead center point of a piston.
The internal combustion engine described in the gazette of Japanese Patent Publication No. Sho 47-43368 has a disadvantage that combustion gas within the sub-combustion chamber does not generate any eddy flow, but may easily be stayed. Scavenging is not carried out sufficiently under a more uniform combustion state in a high load operation range than a laminated combustion state in the low load operation range. In particular, the gas mixture becomes non-uniform and a desired high output is hardly attained due to the fact that a communicating opening communicating the sub-combustion chamber with the main combustion chamber and a central part of the sub-combustion chamber are arranged on a central extended line of the poppet valve.
In addition, the sub-combustion chamber was formed into a substantial cylindrical shape, and fuel in the gas mixture was injected from the poppet valve into the sub-combustion chamber in a substantial cylindrical form in a conical shape opening outwardly from the opening of the poppet valve. Thus, the gas mixture might adhere to the wall surface of the sub-combustion chamber to produce soot in an easy manner. Further, the gas mixture was not sufficiently contacted with the electrode of the spark plug, thereby producing an irregular ignition.